Firefighters in South Australia have mobilised to try and stop a major bushfire that is threatening a town near Port Lincoln.

Firebreaks have been built but the blaze is raging out of control on several fronts and containment is going on round the clock.

For the moment no injuries have been reported but several farming communities have been destroyed and families evacuated. Showers predicted for today may help damp down the fires before they cause more serious damage or loss of life.